Expanded beam array for fiber optics

ABSTRACT

An expanded beam fiber optic array connector includes a ferrule holding ends of optical fibers in a first ordered array. A plurality of lenses packaged into a unitary structure, formed of an optical grade material, different than a material used to form the ferrule, is attached to the ferrule. The lenses are arranged into a second ordered array matching the first ordered array of the ends of the optical fibers. The lenses of the expanded beam connector associated with transmit channels can be constructed with a prescription geared specifically for transmitting light, whereas the lenses of the expanded beam connector associated with receive channels can be constructed with a prescription geared specifically for receiving light.

This application claims the benefit of U.S. Provisional Application No.61/891,348, filed Oct. 15, 2013, and U.S. Provisional Application No.61/992,495, filed May 13, 2014, both of which are herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an expanded beam multi-fiber connector.

2. Description of the Related Art

An MTP/MPO (multi-fiber termination push-on/Multi-fiber Push On) orMT-RJ connector is known in the background art, such as in U.S. Pat. No.6,880,980, which is incorporated herein by reference. Such connectorspresent one or more arrays of polished fiber ends at a front face of theMTP/MPO or MT-RJ connector, as shown in the figures of U.S. Pat. No.6,880,980.

Applicants' prior U.S. Pat. No. 8,393,804, which is incorporated hereinby reference, demonstrated an advantage over the array type connectorshaving polished fiber ends. As shown in FIGS. 13 and 14, a multi-fiberconnector 81 may include pins 83 or alignment holes 85 to assist inmating the multi-fiber connector 81 into an adapter or port. A lens 91,such as spherical lenses 91-1 through 91-8 formed of sapphire, isaffixed at the end of each V-groove 87 (such as V-grooves 87-1 through87-8) for each fiber 89 (such as fibers 89-1 through 89-8) of themulti-fiber connector 81. Hence, the connector 81 is converted into anexpanded beam connector, which has several advantages, as described inmore detail in U.S. Pat. No. 8,393,804.

US Published Patent Application 2009/0154884, which is hereinincorporated by reference, shows a modified expanded beam MT ferrule. Inthe design of US Published Patent Application 2009/0154884, as depictedin FIGS. 15-17, a frame 102 has a front or mating face 103. Guide pinholes 104 are formed in the front face 103. V-grooves 109 holdingoptical fibers 134 are located at a rear portion of the frame 102. Theframe 102 has lenses 106 at the ends of the V-grooves 109. The lenses106 are integrally molded with the frame 102 out of a common material,like a polycarbonate or Ultem (See paragraph 0015, lines 6-8 of USPublished Patent Application 2009/0154884).

Therefore, US Published Patent Application 2009/0154884 offers anadvantage over U.S. Pat. No. 8,393,804 in that the lenses 106 are notseparate elements which must be assembled/adhered to the V-grooves 109,but are rather integrally molded features of the frame 102 adjacent tothe V-grooves 109. Because the lenses 106 are integrally molded, theframe 102 requires “precision machining and tooling” (See paragraph0016, lines 13-14 of US Published Patent Application 2009/0154884). Theother portions of the connector do not require precision machining ortooling, like the housing 112 and boot 124. The housing 112 can beformed of glass filled thermo plastics, such as liquid crystal polymer.The boot 124 may be formed of thermo plastic rubber, such as apolypropylene vulcanization elastomer.

Additional related art may be found in the following documents, each ofwhich is herein incorporated by reference: 2001/0055446; 2002/0118925;2004/0017984; 2006/0245694; 2009/0324175; 2010/0329612; 2012/0014645;2012/0020618; 2012/0155807; 2013/0251315 and WO 2012/106510.

SUMMARY OF THE INVENTION

The Applicant has appreciated drawbacks in the above-describedconnectors of the prior art. For example, precision molding of the frame102 can lead to manufacturing difficulties. Parts must be checked fortolerances, and defective parts must be recycled. The molding equipmentis rather complex with many moving elements, making it expensive tomanufacture. Further, the molding equipment requires added maintenanceto keep tolerances adequate.

Because the lenses 106 are part of the frame 102, the entire frame 102must be molded of a material suitable for the lenses 106, e.g., totransmit light. The single polymer used in the molded multifiberexpanded beam connector ferrules must be free of fillers andcontaminants in order to transmit light consistently. In other words,the polymer used for the frame cannot contain fillers such as glass,carbon or quartz fibers, which are commonly used to form ferrules inorder to provide strength and to reduce thermal expansion/contractionduring environmental temperature changes. The resulting monolithicmolded ferrule including lenses of the prior art design has lessstrength. Also, the ferrule and lens assembly of the prior art hasgreater expansion/contraction and greater change in attenuation duringthermal cycling than ferrules made with “filled” polymers.

Where the lenses are integrally molded, most monolithic multifiberexpanded beam ferrules are molded from polyetherimide. Polyetherimide isa compromise material for light transmittance, strength and coefficientof thermal expansion (CTE). However, polyetherimide has significantabsorption, e.g., 10-20% absorption over the electromagnetic spectrum.To attain sufficient strength using polyetherimide, the component partsare also made thicker. A thicker lens presents more material to absorb,i.e., attenuate, light. Signal losses of 0.25 dB to 0.5 dB per lenstransition are typical.

The signal attenuation through the lens material may lead to a drawbackin that fiber cords employing connectors with the integrally moldedlenses can only run from transceiver to transceiver. In other words, if10-20% of the signal light is absorbed at a first connector attached toa first transceiver and another 10-20% of the signal light is absorbedat the connector at the other end of the fiber cord, the signal has beensignificantly attenuated by the fiber cord. Daisy-chaining fiber cordsbetween transceivers could produce too much attenuation and cause afailure in the communication system. For example, daisy-chaining threefiber cords employing connectors with the integrally molded lenses wouldcause the light signal to pass through six lens formed ofpolyetherimide, with each lens attenuating 10 to 20% of the light signalstrength, e.g., up to a 3 dB signal drop.

Conversely, materials suitable for light transmittance are often timesnot suitable for the connector ferrule parts, e.g., the V-grooves,because of poor thermal expansion characteristics. For example, if theV-grooves are moving, expanding and contracting, during a thermal cycle,the performance of the connector may be impaired. The connector maysuffer attenuation during a portion or portions of the thermal cycle ofthe V-grooves. Contracting or expanding results in pulling or pushingthe fibers in the V-grooves out of optimum alignment with the lenses,and/or stresses the juncture with the optical epoxy, and/or stresses theoptic fibers themselves. This may manifest itself as an erraticconnector, which fails only under certain thermal conditions. Also, whenthe other mating parts of the connector, e.g., the housing and/or theboot, are formed of different materials, e.g., materials impregnatedwith fiber or glass to improve thermal expansion characteristics, thedifference in expansion between the two materials of the connector canlead to mechanical stresses within the connector and to signalattenuation within the connector.

It is an object of the present invention to provide an expanded beammulti-fiber connector, which enjoys the benefits of integrally moldedlens, e.g., reduced assembly time and labor, while avoiding some of thedrawbacks of integrally molded lens, as appreciated by the Applicant anddescribed above.

The Applicant has appreciated that an expanded beam multi-fiberconnector's performance can be enhanced by customizing the lenses of themulti-fiber connector for light transmittance or light reception. Inother words, most multi-fiber connectors have fiber ends dedicated totransmit channels and fiber ends dedicated to receive channels. Forexample, if an eight fiber MPO connector is used in conjunction withfour transceivers, the MPO would typically have four transmit channelsand four receive channels.

The lenses of the expanded beam connector associated with transmitchannels can be constructed with a prescription geared specifically fortransmitting light, whereas the lenses of the expanded beam connectorassociated with receive channels can be constructed with a prescriptiongeared specifically for receiving light. The details will be describedin more detail below.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limits ofthe present invention, and wherein:

FIG. 1 is a perspective view of a fiber optic ferrule, in accordancewith the present invention;

FIG. 1A is a perspective view of a lens array element, in accordancewith the present invention;

FIG. 1B is a close up view of a hole within the lens array element ofFIG. 1A;

FIG. 2 is a side view of the fiber optic ferrule of FIG. 1;

FIG. 2A is a side view of the lens array element of FIG. 1A;

FIG. 3 is a top view of the fiber optic ferrule of FIG. 1;

FIG. 3A is a top view of the lens array element of FIG. 1A;

FIG. 4 is a front view of the expanded beam fiber optic array connectorwith the lens array of FIG. 1A assembled to the fiber optic ferrule ofFIG. 1;

FIG. 5 is a perspective view of a fiber optic ferrule, in accordancewith an alternative embodiment of the present invention;

FIG. 6 is a perspective view of a rear side of a lens array element, inaccordance with an alternative embodiment of the present invention;

FIG. 7 is a perspective view of a fiber optic ferrule and a lens arrayelement, similar to FIGS. 1 and 1A, but showing a two-piece lens arrayelement;

FIG. 8 is a close-up perspective view of a lens portion of FIG. 7;

FIG. 9 is a front view of the lens portion of FIGS. 7 and 8;

FIG. 10 is a front view of a lens portion having a first alternativelens placement arrangement;

FIG. 11 is a front view of a lens portion having a second alternativelens placement arrangement;

FIG. 12 is a perspective view of a frame with a lens placementconsistent with FIGS. 7-9, in accordance with the present invention;

FIG. 13 is a top view of fibers in V-grooves leading up to lenses withinan MT ferrule, in accordance with the prior art;

FIG. 14 is an end view of a mating face of the MT ferrule of FIG. 13;

FIG. 15 is an exploded front perspective view of a lensed MT ferrule, inaccordance with the prior art;

FIG. 16 is an exploded rear perspective view of the lensed MT ferrule ofFIG. 15; and

FIG. 17 is a front perspective view of the fully assembled lensed MTferrule of FIG. 15.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now is described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, thethickness of certain lines, layers, components, elements or features maybe exaggerated for clarity. Broken lines illustrate optional features oroperations unless specified otherwise.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andrelevant art and should not be interpreted in an idealized or overlyformal sense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. As used herein, phrases such as “between X and Y” and“between about X and Y” should be interpreted to include X and Y. Asused herein, phrases such as “between about X and Y” mean “between aboutX and about Y.” As used herein, phrases such as “from about X to Y” mean“from about X to about Y.”

It will be understood that when an element is referred to as being “on”,“attached” to, “connected” to, “coupled” with, “contacting”, etc.,another element, it can be directly on, attached to, connected to,coupled with or contacting the other element or intervening elements mayalso be present. In contrast, when an element is referred to as being,for example, “directly on”, “directly attached” to, “directly connected”to, “directly coupled” with or “directly contacting” another element,there are no intervening elements present. It will also be appreciatedby those of skill in the art that references to a structure or featurethat is disposed “adjacent” another feature may have portions thatoverlap or underlie the adjacent feature.

Spatially relative terms, such as “under”, “below”, “lower”, “over”,“upper”, “lateral”, “left”, “right” and the like, may be used herein forease of description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. It willbe understood that the spatially relative terms are intended toencompass different orientations of the device in use or operation inaddition to the orientation depicted in the figures. For example, if thedevice in the figures is inverted, elements described as “under” or“beneath” other elements or features would then be oriented “over” theother elements or features. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the descriptors ofrelative spatial relationships used herein interpreted accordingly.

FIGS. 1 and 1A are perspective views of a fiber optic ferrule and a lensarray element, respectively, in accordance with the present invention.FIG. 1B is a close up view of a hole within the lens array element ofFIG. 1A. FIGS. 2 and 2A are side views of the fiber optic ferrule andthe lens array element of FIGS. 1 and 1A, respectively. FIGS. 3 and 3Aare top views of the fiber optic ferrule and the lens array element ofFIGS. 1 and 1A, respectively.

FIGS. 1 and 1A; 2 and 2A; and 3 and 3A are exploded views showing thefiber optic ferrule and lens array element as first and second parts,just before assembly. In an assembled state the first and second partsform an expanded beam fiber optic array connector.

FIG. 4 is a front view with the expanded beam fiber optic arrayconnector with lens array of FIG. 1A assembled to the fiber opticferrule of FIG. 1.

Looking at FIGS. 1-4, a first part 11 for holding a plurality of opticalfibers has a first end 13 and a second end 15. The second end 15 isopposite to the first end 13. The first part 11 resembles a typical MTferrule for a typical MTP/MPO connector and may be formed of a polymerimpregnated with a material to provide strength and reduce thecoefficient of thermal expansion (CTE) of the first part 11.

Plural optical fibers enter at the first end 13 of the first part 11 andextend to the second end 15 of the first part 11. Along the length ofthe first part 11, the optical fibers may reside in V-grooves forholding said plural optical fibers in a spaced array, as depicted in theprior art described above. At the second end 15, ends 17-1 through 17-12of the plurality of optical fibers are presented in a first orderedarray at a surface 19 defining the second end 15 of the first part 11.The ends 17-1 through 17-12 may be polished smooth with the surface 19,polished with fiber protrusion relative to surface 19, cleaved orotherwise assembled with protrusion relative to surface 19. Althoughtwelve fibers are illustrated, other numbers of fibers are possible,such as a single row of eight fibers, or two rows of fibers with eightor twelve or sixteen fibers in each row, or three rows of fibers witheight or twelve or sixteen fibers in each row. Basically, the fiber ends17-1 through 17-12 may be arranged in the same manner as shown in theprior art described above. The optical fibers may have any size, such asthe common 125 micron diameter size or uncommon sizes such as an 80micron diameter size.

A second part 21 has a first face 25 and a second face 27, opposite tothe first face 25. The first face 25 of the second part 21 abuts thesecond end 15 and/or the surface 19 of the first part 11, when thesecond part 21 is assembled to the first part 11.

A plurality of lenses 23-1 through 23-12 are formed in the second part21. The plurality of lenses 23-1 through 23-12 are arranged into asecond ordered array matching the first ordered array of the ends 17-1through 17-12 of the optical fibers. Each lens 23-1 through 23-12overlies a respective end 17-1 through 17-12 of one of the plurality ofoptical fibers, when the second part 21 is assembled to the first part11.

In one embodiment, the second part 21 is a unitary structure and isformed of an optical grade material, different than the material used toform the first part 11. For example, the second part 21 may be formed offused silica, fused quartz, sapphire, silicon, other optical glasses oroptical grade polymers. In a preferred embodiment, the second part 21 isentirely formed of optical grade polycarbonate.

A stiffening element or elements 29 and/or 30 may optionally be attachedto the second element 21. The stiffening elements 29 and/or 30 mayextend in a direction substantially perpendicular to a direction 33defined from the first face 25 of the second part 21 to the second face27 of the second part 21, which is also the direction in which theV-grooves holding the optical fibers extend. The stiffening elements 29and/or 30 may be formed as rods, and embedded within a material formingthe second part 21. The stiffening elements 29 and/or 30 improve thecoefficient of thermal expansion (CTE) of the second part 21, by makingthe overall CTE of the second part closer to the CTE of the first part11.

In a preferred embodiment, a first distance 35 is defined from a firstplane 37 encompassing the first end 13 of the first part 11 to a secondplane 39 encompassing the second end 15 of the first part 11. A seconddistance 41 is defined from a third plane 43 encompassing the first face25 of the second part 21 to a fourth plane 45 encompassing the secondface 27 of the second part 21. A sum of the first and second distances35 and 41 is about 8 mm. In other words, the first part 11, whileresembling a typical MT ferrule, actually has a shortened length 35.When the second part 21 is assembled to the first part 11, the combinedlengths 35+41 will be approximately the same as the length, e.g., 8 mm,of a typical MT ferrule.

It is also within the purview of the present invention for the firstpart to be a typical length MT ferrule having a first distance 35equaling about 8 mm. Then, when the second part 21 is assembled to thefirst part 11, the combined lengths 35 and 41 will create an expandedbeam fiber optic array connector having an overall length greater thanthe typical MT ferrule. In other words, the second part 21 may beassembled to the prior art's standard MT ferrule.

To assemble the second part 21 to the first part 11, one embodiment ofthe invention has an optical epoxy attaching each lens 23-1 through23-12 to a respective end 17-1 through 17-12 of one of the plurality ofoptical fibers. Epoxy may also attached other portions of the first face25 of the second part 21 to other portions of the surface 19 of thefirst part 11.

In an alternative embodiment, the second part 21 may be removablyattached to the first part 11 by a friction fit. To this end, a firsthole 47 is formed in the first part 11 for accepting a first guide pin49. A second hole 51 may also be formed in the first part 11 foraccepting a second guide pin (not shown) of a mating connector (notshown). A third hole 53 is formed in the second part 21 for acceptingthe first guide pin 49. A fourth hole 55 is also formed in the secondpart 21 for accepting the second guide pin.

The first guide pin 49 may be held by a pin clamp (FIG. 2) then passedthrough the first and third holes 47 and 53. The third hole 53 mayinclude at least one protruding surface formed on its perimeterextending toward a center of the third hole 53 to create a frictionalengagement with the first guide pin 49. In a preferred embodiment (asshown in FIG. 1B), the third hole 53 includes three evenly spaced flats57-1, 57-2 and 57-3 around its perimeter, with each flat 57 slightlyextending toward the center of the third hole 53. The fourth hole 55 maylikewise include at least one protruding surface 57 formed on itsperimeter extending toward a center of the fourth hole 55 to create africtional engagement with the second guide pin of the first part 11, ifthe first part 11 is formed as a male connector having two guide pins,as shown in FIG. 1 of U.S. Pat. No. 6,880,980, discussed above.

In the embodiment of FIGS. 1-4, the first guide pin 49 is attachedwithin the first part 11 via a pin clamp and extends outwardly from thefirst hole 47 through the third hole 53 for engagement with anotherconnector (not shown). The second guide pin is part of the otherconnector and extends through the fourth hole 55 and into the secondhole 51.

In overall structure, the second part 21 may be viewed as a bezel 59 atleast partially surrounding a lens portion 61 containing the pluralityof lenses 23-1 through 23-12. A forward edge of the bezel 59 defines thesecond face 27 of the second part 21 and extends further away from thesecond end 15 of the first part 11 than any part of the lenses portion61, such that the plurality of lenses 23-1 through 23-12 are recessedinto the second face 27 of the second part 21. By recessing theplurality of lenses 23-1 through 23-12 beneath the second face 27, thelenses 23-1 through 23-12 are protected from abrasion scratches duringmating, e.g., abutment, between the connector faces, and also protectedfrom abrasion scratches should the mated connectors be employed in aharsh environment prone to vibration, e.g., in a land, air or watervehicle.

The above description has shown the second part 21 being formed as aunitary piece. However, the second part 21 could be formed of primarilytwo parts, with the bezel 59 being formed separately from the lensportion 61. In such an instance, the bezel 59 may be formed of adifferent material as compared to the lens portion 61, and/or may beremovable relative to the lens portion 61. For example, the bezel 59 maybe formed of a same material as the first part 11, and the lensesportion 61 may be formed entirely of an optical grade of polycarbonate.

For example, an optical epoxy may attach the lens portion 61 to the ends17-1 through 17-12 of the plurality of optical fibers. Then, after theepoxy cures, the bezel 59 may be separated from the lens portion 61,leaving the lens portion 61 affixed to the second end 15 of the firstpart 11. In this two-piece embodiment, the bezel 59 may serve thepurpose of an alignment tool, whereby the third and fourth holes 53 and55 engage guide pins, e.g., the first pin 49 and a temporary guide pinused for the assembly step, to bring the lens portion 61 into properalignment with the ends 17-1 through 17-12 of the optic fibers beforecuring the optical epoxy to attach each lens 23-1 through 23-12 to theends 17-1 through 17-12 of the optical fiber. If the pins and holesprovide only course alignment, the bezel 59 may be slightly moved ortapped manually while the lenses 23-1 through 23-12 are viewed through amagnifying system or measured through an optical transmittance test toensure correct alignment prior to curing the epoxy. Also, it would bepossible to use manually adjustable features on the bezel 59, e.g., setscrews, to abut the lens portion 61 and move the lens portion 61relative to the bezel 59, e.g., up or down, right or left, while thebezel 59 is relatively fixed in position by the guide pins engagedwithin the third and fourth holes 53 and 55. Adjusting the set screwswithin threaded bores formed within the bezel 59 could slightly move thelens portion 61 to bring its lenses 23-1 through 23-12 into properalignment with the ends 17-1 through 17-12 of the optical fibers, asviewed through a magnifying system or optical transmittance testingsystem.

A method of forming an expanded beam fiber optic array connectorincludes the steps of inserting a plurality of optical fibers into thefirst end 13 of the first part 11 until ends 17-1 through 17-12 of theplurality of optical fibers are approximately flush with the second end15 of the first part 11. Then, cleaving and polishing the ends 17-1through 17-12 of the plurality of optical fibers flush with or slightlyprotruding above the surface 19 defining the second end 15 of the firstpart 11. The cleaving step may be performed mechanically with a blade oralternatively with a laser. Next, abutting the second part 21 over thepolished ends 17-1 through 17-12 of the plurality of optical fibers.Aligning lenses 23-1 through 23-12 within the second part 21 with thepolished ends 17-1 through 17-12 of the plurality of optical fibers. Andfinally, attaching the second part 21 to the first part 11.

The final step of attaching the second part 21 to the first part 11 maybe accomplished by frictionally engaging one or more holes, e.g., thirdand fourth holes 53 and 55, formed in the second part 21 to one or morepins, e.g., first guide pin 49, associated with the first part 11. Ifonly a frictional attachment is used, the second part 21 is removablyattached to the first part 11.

The step of attaching the second part 21 to the first part 11 may alsoinclude curing an epoxy residing between the first and second parts 11and 21. In one embodiment the epoxy is an optical epoxy and also residesbetween the lenses 23-1 through 23-12 and the ends 17-1 through 17-12 ofthe optical fibers, wherein such optical epoxy functions as a waveguideto couple light signals from the ends 17-1 through 17-12 to the lenses23-1 through 23-12 and prevents debris from coming between the ends 17-1through 17-12 and the lenses 23-1 through 23-12.

FIGS. 5 and 6 show an alternative embodiment of the invention, where thesame elements as illustrated in FIGS. 1-4 are labeled with the samereference numerals. In FIG. 5, the first part 11′ has a stepped portion101. The stepped portion 101 extends from the second end 15 of the firstpart 11′. The ends 17-1 through 17-12 of the plurality of optical fibersare approximately flush with, or slightly protruding from, the outerface 19′ of the stepped portion 101. The ends 17-1 through 17-12 of theplurality of optical fibers may be cleaved by a blade/polishing processor by use of a laser.

The second part 21′ includes a recessed portion 143 sized to fit overthe stepped portion 101. A close tolerance in mating of the steppedportion 101 within the recessed portion 143 can help to providealignment between the ends 17-1 through 17-12 of the plurality ofoptical fibers and the lens 23-1 through 23-12. Also, the steppedportion 101 will provide lateral support to the second part 21′ indirections perpendicular to the direction 33, which will help to ensurethat the second part 21′ remains attached to the first part 11′. Tosecure the second part 21′ to the first part 11′, an epoxy may also beapplied between the sidewalls of the stepped portion 101 and thesidewalls of the recessed portion 103.

The Applicant has also appreciated that an expanded beam multi-fiberconnector's performance can be enhanced by customizing the lenses of themulti-fiber connector for light transmittance or light reception. Asmentioned previously, the second part 21 or 21′ could be formed ofprimarily two parts, with the bezel 59 being formed separately from alens portion 61A. In such an instance, the bezel 59 may be formed of adifferent material as compared to the lens portion 61A, and/or may beremovable relative to the lens portion 61A. For example, the bezel 59may be formed of a same material as the first part 11, and the lensesportion 61A may be formed entirely of an optical grade of polycarbonate,or other optical materials as listed above. Such an arrangement isdepicted in FIG. 7.

FIG. 8 is a close-up perspective view of the lens portion 61A of FIG. 7.FIG. 9 is a front view of the lens portion 61A of FIGS. 7 and 8. InFIGS. 7-9, a plurality of lenses 23A-1 through 23A-12 are formed in thelens portion 61A. The plurality of lenses 23A-1 through 23A-12 arearranged into an ordered array matching the ordered array of the ends17-1 through 17-12 of the optical fibers in the first part 11. Each lens23-1 through 23-12 overlies a respective fiber end 17-1 through 17-12 ofone of the plurality of optical fibers, when the lens portion 61A isassembled to the first part 11, in a manner as described above. Thelenses 23 include lenses of a first type, e.g., type A, such as lenses23A-1, 23A-3, 23A-5, 23A-7, 23A-9 and 23A-11. The lenses 23 also includelenses of a second type, e.g., type B, such as lenses 23A-2, 23A-4,23A-6, 23A-8, 23A-10 and 23A-12.

The lenses 23 may be customized for light transmittance or lightreception. For example, type A lenses could be optimized for receiving alight signal, whereas type B lenses could be optimized to transmit alight signal. Lenses 23 may be optimized for transmittance of light orreception of light by having difference prescriptions. The term“different prescriptions” means that a first lens relative to a secondlens intentionally affects light differently. The different prescriptionmay be caused by a different shape, size and/or material content, suchas a different index of refraction.

FIG. 9 shows the transmit and receive channels alternating along theface of the lens portion 61A. When a first expanded beam multi-fiberconnector is mated to a second expanded beam multi-fiber connector, eachtype A lens of the first connector faces to a type B lens of the secondconnector. Likewise, each type B lens of the first connector faces to atype A lens of the second connector. Of course, alternating the transmitand receive channels in the multi-fiber connector is only one example ofa fiber layout.

FIG. 10 illustrates a lens portion 61B wherein the type A lenses may belocated in the lens positions 23B-1 through 23B-6 and the type B lensesmay be located in the lens positions 23B-7 through 23B-12. Type A lensescould be optimized for receiving a light signal, whereas type B lensescould be optimized for transmitting a light signal. Hence, the expandedbeam multi-fiber connector is designed to have receiving fiber ends 17-1through 17-6 ending behind lens positions 23B-1 through 23B-6, andtransmitting fiber ends 17-7 through 17-12 ending behind lens positions23B-7 through 23B-12.

FIG. 11 illustrates a lens portion 62C wherein the type A lenses arelocated in a first row of lens positions 23C-1 through 23C-12 and type Blenses are located in a second row of lens positions 23C-13 through23C-24. Type A lenses could be optimized for receiving light signals,whereas type B lenses could be optimized for transmitting a lightsignal. Hence, the expanded beam multi-fiber connector is designed tohave receiving fiber ends 17-1 through 17-12 ending behind lenspositions 23C-1 through 23C-12, and transmitting fiber ends 17-13through 17-24 ending behind lens positions 23C-13 through 23C-24. Ofcourse, more than two rows of fiber ends 17 and lens 23 may berepresented on the multi-fiber connector's face, such as three rows orsix rows.

In accordance with the present invention, the lens portions 61A, 61B,61C may be formed similar to the lens portion 61 described above, e.g.,may include the stiffening element or elements 29 and/or 30, and maycooperate with the first part 11 or 11′, as described above. Further,the lens portions 61A, 61B, 61C need not be separable from the bezel 59.In other words, the lens portions 61A, 61B, 61C may be integrally formedwith the bezel 59, as a unitary second part 21.

Moreover, benefits of the present invention's customized lensprescriptions could be employed in the structure of US Publishedapplication 2009/0154884 and devices similar thereto, wherein the firstand second parts are unitarily formed of a same material, likePolyetherimide. FIG. 12 depicts the configuration wherein theprescription lenses 23A-1 through 23A-12 for receiving light andtransmitting light are employed in the frame 102 of the 2009/0154884device.

In summary, fiber optic jumpers, patch cords, trunk cables, fanouts andother cable configurations provide optical connectivity in numerousspaces including LANs, WANs, Datacenters, high performance computers,vehicles, aircraft, weapons and ships. Some harsh environment fiberoptic cables use expanded beam optical connectors. Expanded beamconnectors require lower coupling force and are highly insensitive tomechanical shock, dust and vibration. In an expanded beam connectorsystem, an optical fiber core radiates energy into a lens or an array oflenses with spherical or aspherical profiles. The light energy expandsin the lens, exits the opposite side of the lens and travels throughspace to a second, receiving lens. The light energy is focused in thesecond lens and exits the second lens to enter a receiving opticalfiber. Light may also be emitted from LEDs, lasers or other sources andfocused into optical fiber using lenses.

Existing multi-fiber expanded beam connectors are terminated withcomplex time consuming procedures. The steps include:

1) Cleave the ribbonized fibers to produce planar cleaves perpendicularto the fiber axis. (Expensive $75,000 laser cleavers are recommended).

2) Route the fibers into connector v-grooves and through alignmentholes.

3) Remove debris from the fibers cleaves.

4) Repeat steps 1-3 for each row of fibers.

5) Deposit epoxy into the alignment v grooves and epoxy well.

6) Force each fiber cleave against the back of the array lens to removetrapped air and establish launch and focal planes.

7) Hold each of the multiple fibers in position while the epoxy iscured.

The aforementioned termination procedure works best with ribbonizedfiber. Ribbonized fiber bends much easier about an axis perpendicular tothe fiber and parallel to the ribbon than an axis perpendicular to thefiber and ribbon. The linear fiber arrangement is less compact than ahexagonal close packed fiber arrangement and requires more jacketingmaterial. The ribbon fibers larger cross sectional area and strong bendpreference are less desirable than a loose tube close-packed fiber cableconstruction.

Several of the multi-fiber expanded beam connector ferrules are moldedin one piece from a single polymer using a complex mold where the lensprescriptions are in one steel detail mounted to a slide and thev-grooves and fiber alignment holes are in a second steel detail mountedto a second slide. The pins that form the fiber alignment holes sealagainst a third steel detail mounted in the mold A or B plate.Significant effort is required to build and maintain the mold sovariation is held to a few microns.

The single polymer used in the molded multifiber expanded beam connectorferrules must be free of fillers and contaminants to transmit lightconsistently. The polymer cannot contain fillers such as glass, carbonor quartz fibers which commonly provide strength and reduce thermalexpansion in polymers. The resulting monolithic molded ferrule has lessstrength and greater expansion/contraction and greater change inattenuation during thermal cycling than ferrules made with filledpolymers. Most monolithic multifiber expanded beam ferrules are moldedfrom polyetherimide which has significant absorption 10-20% over theelectromagnetic spectrum and thicknesses in use.

The Applicant recognizes the advantages of the expanded beam connectortechnology and disadvantages with current products. The Applicant hasdeveloped an arrayed lens which can mount onto a multi-fiber arrayferrule including, but not limited to MT and MTRJ ferrules. A similar oridentical array lens can be mounted on the receiving MT ferrule to focusthe light into the receiving fiber. The array connectors can haveintegral or separate alignment pins that can be arranged aspinned/unpinned or hermaphroditically.

The proposed lens array may be made from fused silica, fused quartz,sapphire, silicon, other optical glasses or optical grade polymers withor without materials to reduce the coefficient of thermal expansion.Lenses may be spherical, aspherical or Fresnel and may be coated tominimize reflection, water absorption and/or wear.

Lenses may be shaped for on-axis transmittance or for crossing adjacentfiber signals or for splitting and/or combining signals. The lens arraymay locate relative to the fiber using ferrule guide pins holes and/orby active alignment and epoxy to maintain position. The lens array canalso be located within a frame of a second material that aligns toferrule alignment holes/pins. The frame may remain on the ferruleassembly or be removed. The frame may have circular holes/pins or holeswith flats to interfere with guide pin clearance. Ferrule alignmentguide pin holes may be sleeved with a protruding sleeve that is used toalign the array. An index material, liquid, epoxy, gel, rigid orsemi-rigid material may be placed between the fibers and lens and/orbetween the lenses to minimize reflection, indirect light and/or sealout contamination.

The array lens may be sized to fit onto a shortened array connectorferrule to fit into standard connector housings. The array ferrule canbe of a standard dimension, shortened along the fiber axis, equippedwith fiber stubs and index matching material or equipped with fiberstubs for fusion splicing.

The proposed new expanded beam array ferrule design allows:

1) Lenses to be fabricated from numerous materials including glasses,polymers, sapphire and silicon.

2) The manufacturer may terminate, polish, test and inspect the arrayferrule using ribbonized or loose tube fiber, standard tools andprocedures before adding an array lens.

3) A user may add array lenses to any new or existing multi-fiberferrule.

The arrayed lens portion 61A, 61B, 61C utilizes lenses that are ofsimilar but different prescriptions in order to more efficientlytransmit and focus the light energy across space and through theopposite (receiving) lens. The lenses can be ordered in severalvariations on the array (such as every-other lens in a row, all lensesin a single row, some lenses on a row with others in the same row, orany variation thereof) and in either single or multiple rows of lenses.

The transmitting lens can be of different substrate material (such asFused Silica, Sapphire, Multi-Spectral Zinc Sulfide, etc.) than thereceiving lens.

The arrays can mount onto a multi-fiber array ferrule including, but notlimited to MT and MTRJ ferrules. The array connectors can have integralor separate alignment pins that can be arranged pinned/unpinned orhermaphroditically.

The proposed lens array may be made from fused silica, fused quartz,sapphire, silicon, other optical glasses or optical grade polymers withor without materials to reduce the coefficient of thermal expansion.Lenses may be spherical, aspherical or Fresnel and may be coated tominimize reflection, water absorption and/or wear.

Lenses may be shaped for on axis transmittance or for crossing adjacentfiber signals or for splitting and/or combining signals.

The lens array may locate relative to the fiber using ferrule guide pinsholes and/or by active alignment and epoxy to maintain position and/orby utilizing Photolithography to create a pattern or indicator mark foralignment or assembly purposes. The lens array can also be locatedwithin a frame of a second material that aligns to ferrule alignmentholes/pins. The frame may remain on the ferrule assembly or be removed.The frame may have circular holes/pins or holes with flats to interferewith guide pin clearance. Ferrule alignment guide pin holes may besleeved with a protruding sleeve that is used to align the array.

An index material, liquid, epoxy, gel, rigid or semi-rigid material maybe placed between the fibers and lens and/or between the lenses tominimize reflection, indirect light and/or seal out contamination.

The proposed new expanded beam array ferrule design allows the lenses orlens array can be fabricated so the prescriptions of the transmittinglenses or lens array can be either identical or different from thereceiving lens or array; and the transmitting lens or lens array can beof either identical or different material from the receiving lens orlens array.

The Lens Configuration Differences Matrix below shows the overallperformance (tolerance) improvement for the different parameters. TheSpot Size is the most significant parameter, but Angle Reduction isimportant as well.

Transmitting Receiving Percent Percent Lens Lens Lens Spot Size AngleFocus Percent Configuration Material Material Reduction ReductionDistance Transmittance Identical Fused Silica Fused  0% 15% 200 um99.44% Silica Asymmetric Sapphire Sapphire 16% 15% 360 um 99.15%Asymmetric Sapphire Fused 20% 27% 230 um 99.38% Silica

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are to beincluded within the scope of the following claims.

The invention claimed is:
 1. A fiber optic ferrule comprising: a firstpart for holding a plurality of optical fibers, said first part having afirst end and a second end, wherein said second end is opposite to saidfirst end; a plurality of optical fibers entering at said first end ofsaid first part and extending to said second end of said first part,wherein ends of said plurality of optical fibers are approximately flushor slightly protruding along a surface defining said second end of saidfirst part; a second part having a first face and a second face, whereinsaid first face of said second part abuts said second end of said firstpart, and wherein said second face is opposite to said first face; and aplurality of lenses formed in said second part, wherein each lens ofsaid plurality of lenses overlies a flush or protruding end of one ofsaid plurality of optical fibers, wherein said plurality of lensesincludes lenses of different prescriptions and wherein said plurality oflenses includes a first set of lenses having a same first prescriptionoptimized to receive light from an optical fiber end and transmit lightaway from the lens and a second set of lenses having a same secondprescription, different from the first prescription, optimized toreceive light into the lens and focus light onto an optical fiber end,wherein said second part is formed of a bezel at least partiallysurrounding a lenses portion containing said plurality of lenses,wherein an optical epoxy attaches each lens of said plurality of lensesto an end of one of said plurality of optical fibers, wherein said bezelis separable from said lens portion, and wherein said bezel is removedafter said lens portion is affixed to said second end of said firstpart.
 2. The fiber optic ferrule of claim 1, wherein said first part isformed of a polymer impregnated with a material to provide strength andreduce the coefficient of thermal expansion of said first part.
 3. Thefiber optic ferrule of claim 1, wherein said second part is formed offused silica, fused quartz, sapphire, silicon, other optical glasses oroptical grade polymers.
 4. The fiber optic ferrule of claim 1, wherein afirst distance is defined from a first plane of said first end of saidfirst part to a second plane of said second end of said first part, asecond distance is defined from a third plane of said first face of saidsecond part to a fourth plane of said second face of said second part,and wherein a sum of said first and second distances is 8 mm.
 5. Thefiber optic ferrule of claim 1, further comprising: a first hole formedin said first part for accepting a first guide pin; a second hole formedin said first part for accepting a second guide pin; a third hole formedin said second part for accepting the first guide pin; a fourth holeformed in said second part for accepting the second guide pin; and afirst guide pin passing through said first and third holes.
 6. The fiberoptic ferrule of claim 5, wherein said third hole includes at least oneprotruding surface formed on its perimeter extending toward a center ofsaid third hole to create a frictional engagement with said first guidepin.
 7. The fiber optic ferrule of claim 6, wherein said first guide pinis attached within said first part and extends outwardly from said firsthole through said third hole for engagement with another fiber opticconnector, and wherein the second guide pin is part of the another fiberoptic connector and extends through said fourth hole and into saidsecond hole.
 8. The fiber optic ferrule of claim 1, wherein said lensportion is adjustable in its position relative to said bezel.
 9. A fiberoptic ferrule comprising: a first part for holding a plurality ofoptical fibers, said first part having a first end and a second end,wherein said second end is opposite to said first end; a plurality ofoptical fibers entering at said first end of said first part andextending in a first direction to said second end of said first part,wherein ends of said plurality of optical fibers are approximately flushor slightly protruding along a surface defining said second end of saidfirst part; a second part having a first face and a second face, whereinsaid first face of said second part abuts said second end of said firstpart, and wherein said second face is opposite to said first face; aplurality of lenses formed in said second part, wherein each lens ofsaid plurality of lenses overlies a flush or protruding end of one ofsaid plurality of optical fibers; and a stiffening element having alength and a width, wherein the length is longer than the width, andwherein said stiffening element is embedded within a material formingsaid second part and the length of said stiffening element extends in asecond direction substantially perpendicular to the first direction. 10.The fiber optic ferrule of claim 9, wherein said stiffening element is arod.
 11. A fiber optic ferrule comprising: a first part for holding aplurality of optical fibers, said first part having a first end and asecond end, wherein said second end is opposite to said first end; aplurality of optical fibers entering at said first end of said firstpart and extending to said second end of said first part, wherein endsof said plurality of optical fibers are approximately flush or slightlyprotruding along a surface defining said second end of said first part;a second part having a first face and a second face, wherein said firstface of said second part abuts said second end of said first part, andwherein said second face is opposite to said first face; and a pluralityof lenses formed in said second part, wherein each lens of saidplurality of lenses overlies a flush or protruding end of one of saidplurality of optical fibers, wherein said second part is formed of abezel at least partially surrounding a lenses portion containing saidplurality of lenses and said lens portion is adjustable in its positionrelative to said bezel.
 12. The fiber optic ferrule of claim 11, whereinsaid first part is formed of a polymer impregnated with a material toprovide strength and reduce the coefficient of thermal expansion of saidfirst part.
 13. The fiber optic ferrule of claim 11, wherein said secondpart is formed of fused silica, fused quartz, sapphire, silicon, otheroptical glasses or optical grade polymers.
 14. The fiber optic ferruleof claim 11, further comprising: a stiffening element attached to saidsecond part and extending in a direction substantially perpendicular toa direction defined from said first face of said second part to saidsecond face of said second part.
 15. The fiber optic ferrule of claim14, wherein said stiffening element is a rod, embedded within a materialforming said second part.
 16. The fiber optic ferrule of claim 11,wherein a first distance is defined from a first plane of said first endof said first part to a second plane of said second end of said firstpart, a second distance is defined from a third plane of said first faceof said second part to a fourth plane of said second face of said secondpart, and wherein a sum of said first and second distances is 8 mm. 17.The fiber optic ferrule of claim 11, further comprising: an opticalepoxy attaching each lens of said plurality of lenses to an end of oneof said plurality of optical fibers.
 18. The fiber optic ferrule ofclaim 11, further comprising: a first hole formed in said first part foraccepting a first guide pin; a second hole formed in said first part foraccepting a second guide pin; a third hole formed in said second partfor accepting the first guide pin; a fourth hole formed in said secondpart for accepting the second guide pin; and a first guide pin passingthrough said first and third holes.